Silicone adhesive composition, adhesive tape, and method for producing adhesive tape

ABSTRACT

A silicone adhesive composition includes 100 parts by weight of a peroxide-curable silicone, 1.2 to 3.2 parts by weight of an organic peroxide curing agent, and 2 to 9 parts by weight of an addition reaction-curable silicone rubber. An adhesive tape includes a base and an adhesive layer placed on the base, the adhesive layer being formed from the above silicone adhesive composition. The adhesive composition exhibits high load bearing capacity even in higher-temperature environments than ever before. The adhesive tape exhibits high load bearing capacity and good shelf life even in such high-temperature environments.

TECHNICAL FIELD

The present invention relates to a silicone adhesive composition, anadhesive tape, and a method for producing an adhesive tape.

BACKGROUND ART

Known adhesives (pressure-sensitive adhesives) include adhesives basedon silicones (silicone adhesives). Silicone adhesives are superior toacrylic adhesives and rubber adhesives in properties such as heatresistance, cold resistance, weather resistance, chemical resistance,and electrical insulation, and adhere well to various adherends.Silicone adhesives are thus used in various adhesive tapes such asheat-resistant tapes, electrically-insulating tapes, heat sealing tapes,and plating masking tapes. When an adhesive tape is used in anapplication that requires heat resistance, a base with excellent heatresistance such as a fluororesin base or a glass cloth base impregnatedwith a fluororesin is often used with the silicone adhesives. Siliconeadhesives include peroxide-curable adhesives and additionreaction-curable adhesives.

To increase the heat resistance of an adhesive tape, not only theproperties of a base but also those of a silicone adhesive need to beimproved. In view of applications of the adhesive tape, it is desired toimprove, in particular, the ability to maintain the adhesive strength inhigh-temperature environments (load bearing capacity in high-temperatureenvironments) among the properties of the silicone adhesive. PatentLiterature 1 (JP 2010-6918 A) discloses a peroxide-curable siliconeadhesive composition, the composition capable of maintaining itsadhesive strength even at a high temperature above 150° C.

CITATION LIST Patent Literature

-   Patent Literature 1: JP 2010-006918 A

SUMMARY OF INVENTION Technical Problem

An object of the present invention is to provide: a silicone adhesivecomposition that exhibits high load bearing capacity even inhigher-temperature environments than ever before; and an adhesive tapethat exhibits high load bearing capacity and good shelf life even insuch high-temperature environments.

Solution to Problem

The silicone adhesive composition according to the present inventionincludes 100 parts by weight of a peroxide-curable silicone, 1.2 to 3.2parts by weight of an organic peroxide curing agent, and 2 to 9 parts byweight of an addition reaction-curable silicone rubber.

The adhesive tape according to the present invention includes a base andan adhesive layer placed on the base, the adhesive layer being formedfrom the above silicone adhesive composition according to the presentinvention.

The method for producing an adhesive tape according to the presentinvention includes heating an original tape including a base and theabove silicone adhesive composition according to the present inventionplaced on the base and thereby forming the composition into an adhesivelayer, so as to obtain an adhesive tape including the base and theadhesive layer placed on the base.

In another aspect, the method for producing an adhesive tape accordingto the present invention includes: heating a transfer base on which thesilicone adhesive composition according to the present invention isplaced and thereby forming the composition into an adhesive layer; andtransferring the adhesive layer from the transfer base to a base so asto obtain an adhesive tape including the base and the adhesive layerplaced on the base.

Advantageous Effects of Invention

With the present invention, it is possible to obtain: a siliconeadhesive composition that exhibits high load bearing capacity even inhigher-temperature environments than ever before; and an adhesive tapethat exhibits high load bearing capacity and good shelf life even insuch high-temperature environments.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view schematically showing an example of theadhesive tape according to the present invention.

FIG. 2 is a diagram schematically showing the steps of an example of themethod for producing an adhesive tape according to the presentinvention.

FIG. 3 is a diagram schematically showing the steps of another exampleof the method for producing an adhesive tape according to the presentinvention.

DESCRIPTION OF EMBODIMENTS

A silicone adhesive composition according to the present inventionincludes 100 parts by weight of a peroxide-curable silicone, 1.2 to 3.2parts by weight of an organic peroxide curing agent, and 2 to 9 parts byweight of an addition reaction-curable silicone rubber. This compositionexhibits high load bearing capacity even in higher-temperatureenvironments than ever before, such as in an environment with atemperature above 200° C. Additionally, when an adhesive tape is formedusing this composition, the adhesive tape exhibits high load bearingcapacity and good shelf life even in such high-temperature environmentsas mentioned above.

The peroxide-curable silicone includes a peroxide-curable siliconerubber and/or a partial condensate thereof. The silicone rubber may be araw rubber (gum). The peroxide-curable silicone may include at least oneselected from a silicone resin and a partial condensate thereof. Thecomposition of the peroxide-curable silicone is not particularlylimited, as long as the peroxide-curable silicone includes aperoxide-curable silicone rubber and/or a partial condensate thereof.

The peroxide-curable silicone rubber is not particularly limited, andis, for example, an organopolysiloxane having dimethylsiloxane as a mainconstitutional unit. A hydroxy group or another functional group may beintroduced into the organopolysiloxane where necessary. A specificexample of the organopolysiloxane is dimethylpolysiloxane. Theweight-average molecular weight of the organopolysiloxane is typically180,000 or more, preferably 280,000 to 1,000,000, and more preferably500,000 to 900,000. The peroxide-curable silicone may include two ormore peroxide-curable silicone rubbers or may include two or morepartial condensates of peroxide-curable silicone rubbers.

The silicone resin is not particularly limited and is, for example, anorganopolysiloxane having at least one unit selected from an M unit(R₃SiO_(1/2)), a Q unit (SiO₂), a T unit (RSiO_(3/2)), and a D unit(R₂SiO). Rs in these units are each independently a monovalenthydrocarbon group or a hydroxy group. A functional group may beintroduced into this copolymer where necessary, and the introducedfunctional group may be one that undergoes a cross-linking reaction. Itis preferable for the silicone resin to be a so-called MQ resinconstituted by the M units and the Q units.

When the silicone resin is an MQ resin, a molar ratio between thecontent of the M units and the content of the Q units in the resin is,for example, 0.3:1 to 1.5:1, preferably 0.5:1 to 1.3:1, as expressed byM units:Q units.

The peroxide-curable silicone may include two or more silicone resins ormay include two or more partial condensates of silicone resins.

When the peroxide-curable silicone includes a silicone resin, the weightratio between the silicone rubber and the silicone resin in the siliconeis not particularly limited and is, for example, 100:110 to 100:220,preferably 100:160 to 100:190, as expressed by silicone rubber:siliconeresin. When the peroxide-curable silicone includes a partial condensateof a silicone rubber and/or a partial condensate of a silicone resin,the above weight ratio can be determined from the weights of thesilicone rubber and the silicone resin that have yet to undergo partialcondensation.

The organic peroxide curing agent is not particularly limited. Examplesof the curing agent include benzoyl peroxide, t-butyl peroxybenzoate,dicumyl peroxide, t-butylcumyl peroxide, di-t-butyl peroxide,2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,4-dichlorobenzoyl peroxide,1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, and2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3.

The amount of the organic peroxide curing agent included in the siliconeadhesive composition according to the present invention is 1.2 to 3.2parts by weight, preferably 1.4 to 3.0 parts by weight, per 100 parts byweight of the peroxide-curable silicone. When the amount of the curingagent falls below 1.2 parts by weight which is the lower limit, the bondstrength of the adhesive composition becomes insufficient. When theamount of the curing agent exceeds 3.2 parts by weight which is theupper limit, the load bearing capacity in the high-temperatureenvironments is reduced, which results in, for example, a failure toobtain an adhesive tape that exhibits high load bearing capacity andgood shelf life even in the high-temperature environments.

The silicone adhesive composition according to the present invention mayinclude two or more organic peroxide curing agents.

The silicone adhesive composition according to the present inventionincludes an addition reaction-curable silicone rubber. The siliconerubber may be a raw rubber (gum). The addition reaction-curable siliconerubber is not particularly limited, and a well-known additionreaction-curable silicone rubber can be used.

The amount of the addition reaction-curable silicone rubber included inthe silicone adhesive composition according to the present invention is2 to 9 parts by weight, preferably 3 to 7 parts by weight, per 100 partsby weight of the peroxide-curable silicone. When the amount of theaddition reaction-curable silicone rubber is in this range, the siliconeadhesive composition can exhibit high load bearing capacity even in thehigh-temperature environments. When the amount of the additionreaction-curable silicone rubber falls below 2 parts by weight which isthe lower limit, the load bearing capacity in the high-temperatureenvironments is reduced and, in particular, displacement of an adhesivesurface becomes more likely to occur in the high-temperatureenvironments. When the amount of the addition reaction-curable siliconerubber exceeds 9 parts by weight which is the upper limit, the loadbearing capacity in the high-temperature environments is reduced and, inparticular, the bond strength in the high-temperature environments isreduced.

The addition reaction-curable silicone rubber is not particularlylimited, and a well-known addition reaction-curable silicone rubber canbe used. The addition reaction-curable silicone rubber contains anaddition-polymerizable group, and this group is, for example, a vinylgroup.

The silicone adhesive composition according to the present invention mayinclude two or more addition reaction-curable silicone rubbers.

It is preferable that the addition reaction-curable silicone rubber,when cured, have an elastic modulus (storage elastic modulus G′) of 0.01MPa or more and 1 MPa or less at ordinary temperature (25° C.) and havean elastic modulus of 0.01 MPa or more and 1 MPa or less at 200° C. Itis more preferable that the elastic modulus be 0.1 MPa or more and 1 MPaor less at ordinary temperature and be 0.1 MPa or more and 1 MPa or lessat 200° C. The storage elastic modulus G′ can be measured with arheometer. A specific example of the measurement method is to subject ameasurement object to shaping or lamination so that it attains athickness of about 1.5 mm and then perform measurement on the objectusing a rheometer (for example, Advanced Rheometric Expansion System(ARES) manufactured by Rheometric Scientific Inc.) over the temperaturerange from −20° C. to 250° C. under the following measurementconditions: shear mode, frequency=1 Hz, temperature increase rate=5°C./min.

The silicone adhesive composition according to the present inventioncan, where necessary, include another component other than theperoxide-curable silicone, the organic peroxide curing agent, and theaddition reaction-curable silicone rubber, and examples of the anothercomponent include an additive, a catalyst, a cross-linking agent, and asolvent for adjusting the viscosity of the adhesive composition. Thecatalyst is, for example, a platinum catalyst. The cross-linking agentis, for example, a siloxane-based cross-linking agent having a SiHgroup.

The gel fraction of a cured product of the silicone adhesive compositionaccording to the present invention (the gel fraction of an adhesivelayer obtained from the silicone adhesive composition according to thepresent invention) is preferably 40 to 60% and more preferably 45 to55%. The gel fraction of a cured product of the adhesive composition canbe determined, for example, by the following procedures using immersionto dissolve components of the adhesive layer other than the gel.

About 0.1 g of a cured product of the adhesive composition, such as anadhesive layer taken from an adhesive tape, was wrapped by a porouspolytetrafluoroethylene (PTFE) sheet with an average pore diameter of0.2 μm (an example of which is NTF 1122 manufactured by NITTO DENKOCORPORATION), and the wrapping sheet is then bound with a kite string toprepare a measurement sample. Next, the weight of the measurement sampleprepared is measured, and the measured weight is defined as apre-immersion weight C. The pre-immersion weight C corresponds to thetotal weight of the adhesive layer, the polytetrafluoroethylene sheet,and the kite string. The total weight of the PTFE sheet and the kitestring is separately measured beforehand and is defined as a wrappingweight B. Next, the measurement sample is placed in a toluene-filledcontainer having an inner volume of 50 mL and allowed to stand at 23° C.for 7 days. Next, the interior of the container, together with themeasurement sample, is washed with ethyl acetate. The measurement sampleis then taken out of the container, moved into an aluminum cup, anddried at 130° C. for 2 hours to remove ethyl acetate. Next, the weightof the measurement sample from which ethyl acetate has been removed ismeasured, and the measured weight is defined as a post-immersion weightA. The gel fraction can be determined by the following equation.Gel fraction(weight %)=(A−B)/(C−B)×100

The silicone adhesive composition according to the present invention canbe produced, for example, by mixing the peroxide-curable silicone, theorganic peroxide curing agent, and the addition reaction-curablesilicone rubber. The order in which these components are added is notlimited. In this mixing, an additive as mentioned above may be addedwhere necessary. When the silicone is composed of a plurality ofmaterials, the silicone may be formed using the materials and then mixedwith the other components, or the materials themselves may be mixed withthe other components without formation of the silicone so as to producethe silicone adhesive composition according to the present invention.

The silicone adhesive composition according to the present invention canbe used for an adhesive layer of an adhesive tape. In this case, it ispossible to obtain an adhesive tape that exhibits high load bearingcapacity and good shelf life in the high-temperature environments. Suchan adhesive tape is suitable, for example, for use in heat sealing, moreparticularly for use as a release tape (heat sealing tape) forpreventing direct contact between an object to be sealed and a heatingportion of a heat sealing apparatus. The heat sealing tape, which isused by being attached to the heating portion of the apparatus, isusually subjected to a great force acting in such a direction as tolaterally displace the tape on the heating portion every time thesealing operation is repeated. In addition, replacement of the heatsealing tape on the heating portion, which is needed after a certainnumber of heat sealing operations, may be immediately followed bystarting heat sealing again by heating of the heating portion, givingrise to peeling of an edge of a tape newly attached to the heatingportion.

When used in an adhesive tape, the silicone adhesive compositionaccording to the present invention is a silicone adhesive compositionfor (an adhesive layer of) an adhesive tape. The silicone adhesivecomposition according to the present invention is not limited to use in(an adhesive layer of) an adhesive tape and can be used in the sameapplications as conventional silicone adhesive compositions.

FIG. 1 shows an example of the adhesive tape according to the presentinvention. An adhesive tape 1 of FIG. 1 includes a base 2 and anadhesive layer 3 placed on the base 2, the adhesive layer 3 being formedfrom the silicone adhesive composition according to the presentinvention. The adhesive layer 3 is a cured layer of the siliconeadhesive composition according to the present invention.

As the base there can be used any of various bases conventionally usedin adhesive tapes. In view of the heat resistance required of adhesivetapes, it is preferable to use a base made of a heat-resistant material.Examples of the heat-resistant material include polytetrafluoroethylene(PTFE), polyvinylidene fluoride, polyvinyl fluoride,ethylene-tetrafluoroethylene copolymer, a glass cloth, a glass clothimpregnated with PTFE, and polyimide. In an example, the base is a glasscloth base impregnated with PTFE. In this case, the heat resistance ofthe adhesive tape and the releasability of its surface (an exposedsurface of the base) opposite from the adhesive surface can beparticularly high. Such an adhesive tape having high releasability isparticularly suitable for use on a heating portion for heat sealing (foruse as a heat sealing tape).

The glass cloth base impregnated with PTFE can be formed, for example,by immersing a glass cloth in a PTFE dispersion and then heating theglass cloth to a temperature equal to or higher than the melting pointof PTFE.

The thickness of the base is not particularly limited and is, forexample, about 0.005 to 0.3 mm.

The adhesive tape may be in the form of a roll obtained by rolling up asheet-shaped base on which the above adhesive layer is placed.

The adhesive tape according to the present invention can be produced,for example, by the method for producing an adhesive tape according tothe present invention.

In the method for producing an adhesive tape according to the presentinvention, the silicone adhesive composition according to the presentinvention is applied onto a base or a transfer base to form a coatinglayer made of the composition. For the formation of the coating layer, awell-known coating technique can be used. Examples of the coatingtechnique include: coating using various coaters such as a comma coater,a lip coater, a roll coater, a die coater, a knife coater, a bladecoater, a rod coater, a kiss coater, and a gravure coater; screencoating; immersion coating; and cast coating. It is preferable to applythe silicone adhesive composition so that the thickness of the coatinglayer is about 2 to 200 μm, particularly about 10 to 100 μm.

FIG. 2 shows an example of the method for producing the adhesive tapeaccording to the present invention by applying a silicone adhesivecomposition onto a base. In the example shown in FIG. 2, the siliconeadhesive composition according to the present invention is applied ontothe base 2 to form a coating layer 4 (see (a)), then an original tape 5having the base 2 and the coating layer 4 on the base 2 is heated toform the coating layer 4 into the adhesive layer 3, and thus theadhesive tape 1 is obtained (see (b)).

FIG. 3 shows an example of the method for producing the adhesive tapeaccording to the present invention by applying a silicone adhesivecomposition onto a transfer base. In the example shown in FIG. 3, thesilicone adhesive composition according to the present invention isapplied onto a transfer base 6 to form the coating layer 4 (see (a)),and then the transfer base 6 and the coating layer 4 on the transferbase 6 are heated to form the coating layer 4 into the adhesive layer 3(see (b)). Next, the adhesive layer 3 formed is transferred from thetransfer base 6 to the base 2, and thus the adhesive tape 1 is obtained(see (c)).

The base is as described above for the adhesive tape according to thepresent invention.

As the transfer base there can be used, for example, a film or a sheetmade of polyimide, polyethylene, or polypropylene. It is preferable thatthe surface of the transfer base onto which the adhesive composition isapplied be provided with a coating for release which is formed of, forexample, fluorinated silicone.

When the adhesive composition is applied onto a base, the surface of thebase onto which the composition is applied may be surface-treatedbeforehand. The surface treatment of the base is, for example, atreatment for improving the bonding property (anchoring force) betweenthe surface of the base and the adhesive composition applied on thesurface.

Subsequently, the coating layer formed is heat-treated at a temperatureat which curing of the peroxide-curable silicone and the additionreaction-curable silicone rubber contained in the layer proceeds, andthus the adhesive layer is formed. The temperature of the heat treatmentis not limited as long as it is a temperature which allows curing ofboth the silicone and the silicone rubber to proceed. The temperatureis, for example, 100 to 250° C. and preferably 150 to 250° C. The lengthof time of the heat treatment is, for example, 30 seconds to 10 minutes.

The heat treatment converts the coating layer to the adhesive layer.Thus, if the coating layer is formed first on a base, an adhesive tapeincluding the base and an adhesive layer placed on the base can beobtained in the above manner. In the case where the coating layer isformed on a transfer base, an adhesive tape including a base and anadhesive layer placed on the base can be obtained by the formation ofthe adhesive layer by heat treatment, followed by transfer of the formedadhesive layer from the transfer base to the base.

EXAMPLES

Hereinafter, the present invention will be described in more detail withreference to examples. The present invention is not limited to theexamples given below.

Methods for evaluating adhesive tapes fabricated in the examples will bedescribed first.

[Amount of Displacement in Shear Direction in High-TemperatureEnvironment]

Each of the adhesive tapes fabricated was cut to obtain a 10-mm-widetest specimen, which was then attached to a lower edge portion of avertically-held stainless steel plate so that the adhesive area was 10mm×20 mm. This was done in such a manner that the length direction ofthe test specimen coincided with the vertical direction and that thelower edge of the test specimen was not in contact with the stainlesssteel plate. Next, a load of 500 g acting vertically downward wasapplied to the lower edge of the test specimen, and the specimen and theplate were kept as such at 230° C. for 1 hour, after which the amount ofdisplacement of the test specimen was evaluated with a microscope.

[Amount of Peel in 90° Direction in High-Temperature Environment]

Each of the adhesive tapes fabricated was cut to obtain a 10-mm-widetest specimen, which was then attached to a stainless steel plate sothat the adhesive area was 10 mm×20 mm. This was done in such a mannerthat one edge of the test specimen was not in contact with the stainlesssteel plate. Next, a load of 20 g acting in a direction perpendicular tothe surface of the stainless steel plate was applied to the one edge ofthe test specimen, and the specimen and the plate were quickly heated to250° C. and kept as such for 1 hour, after which the amount of peel ofthe test specimen was evaluated.

[Storage Test]

Each of the adhesive tapes fabricated was stored at 60° C. for 7 days,then cooled to ordinary temperature, and subjected to the aboveevaluations of the amount of displacement in the shear direction in ahigh-temperature environment and the amount of peel in the 90° directionin a high-temperature environment.

Example 1

There were mixed: 100 parts by weight of dimethylpolysiloxane(weight-average molecular weight=700,000, raw rubber-like form); 170parts by weight of an MQ resin as a silicone resin (weight-averagemolecular weight=5500), the MQ resin consisting of 44 mol % of(CII₃)₃SiO_(1/2) units corresponding to the M units and 56 mol % of SiO₂units corresponding to the Q units; and toluene. Next, the resultingmixture was held at 100 to 120° C. for 4 hours to allow thedimethylpolysiloxane and the MQ resin to undergo partial condensation.After that, toluene was further added to adjust the content of solids(non-volatile components). This yielded a toluene solution A(concentration of 60 weight %) of the dimethylpolysiloxane, the MQresin, and partial condensates of the dimethylpolysiloxane and the MQresin. The solution A obtained was viscous, colorless, and transparent.

Next, there were mixed 100 parts by weight of the obtained toluenesolution A, 0.96 parts by weight (in terms of solid content) of a xylenesolution of benzoyl peroxide as an organic peroxide curing agent (NYPERBMT-K40, manufactured by NOF CORPORATION and having a solid content of40 weight %), and 5 parts by weight of RTV 4086 (manufactured by DowCorning Toray Co., Ltd.) as an addition reaction-curable siliconerubber. Further, the concentration was adjusted with toluene, and thus asilicone adhesive composition having a concentration of 40 weight % wasobtained.

Next, the silicone adhesive composition obtained was applied to apolyimide film (Kapton 10011, manufactured by DU PONT-TORAY CO., LTD.)serving as a base, and a coating layer with a thickness of 40 μm wasthus formed. Subsequently, the base and the coating layer were heatedtogether using a drying machine held at 200° C. for 3 minutes to curethe coating layer and thus obtain an adhesive tape including the baseand an adhesive layer placed on a surface of the base, the adhesivelayer being formed from the applied adhesive composition.

Example 2

An adhesive tape was obtained in the same manner as in Example 1, exceptthat the amount of the xylene solution of benzoyl peroxide to be mixedwas changed to 1.5 parts by weight in terms of solid content.

Comparative Example 1

An adhesive tape was obtained in the same manner as in Example 1, exceptthat the addition reaction-curable silicone rubber was not mixed.

Comparative Example 2

An adhesive tape was obtained in the same manner as in Example 1, exceptthat the amount of the xylene solution of benzoyl peroxide to be mixedwas changed to 2.1 parts by weight in terms of solid content and thatthe addition reaction-curable silicone rubber was not mixed.

Comparative Example 3

An adhesive tape was obtained in the same manner as in Example 1, exceptthat the amount of the addition reaction-curable silicone rubber to bemixed was changed to 0.6 parts by weight.

Comparative Example 4

An adhesive tape was obtained in the same manner as in Example 1, exceptthat the amount of the xylene solution of benzoyl peroxide to be mixedwas changed to 1.5 parts by weight in terms of solid content and thatthe amount of the addition reaction-curable silicone rubber to be mixedwas changed to 6.0 parts by weight.

In all of Example 2 and Comparative Examples 1 to 4, the concentrationof the silicone adhesive composition obtained during the fabrication ofthe adhesive tape was 40 weight % as in Example 1.

Table 1 below shows the amounts of the organic peroxide curing agent andthe addition reaction-curable silicone rubber mixed in the siliconeadhesive compositions fabricated in Examples 1 and 2 and ComparativeExamples 1 to 4 and also shows the results of evaluation of theproperties of the adhesive tapes. It should be noted that the amounts ofthe organic peroxide curing agent and the addition reaction-curablesilicone rubber in Table 1 are those calculated per 100 parts by weightof the total amount of the peroxide-curable silicone rubber, thesilicone resin, and the partial condensates of the silicone rubber andthe silicone resin in the toluene solution A.

TABLE 1 Comparative Comparative Comparative Comparative Example 1Example 2 Example 1 Example 2 Example 3 Example 4 Organic peroxide 1.62.5 1.6 3.5 1.6 2.5 curing agent (parts by weight) Additional 8.3 8.3 00 1.0 10 reaction-curable silicone rubber (parts by weight) Amount of0.2 0.1 0.9 0.1 0.7 0.1 displacement in shear direction inhigh-temperature environment (mm) Amount of peel in 0 0 0 10 0 30 90°direction in high-temperature environment (mm) Amount of 0.2 0.1 0.8 0.10.6 0.1 displacement in shear direction in high-temperature environment(after storage; mm) Amount of peel in 0 0 0 80 0 45 90° direction inhigh-temperature environment (after storage; mm)

The present invention may be embodied in other forms without departingfrom the spirit or essential characteristics thereof. The embodimentsdisclosed in this specification are to be considered in all respects asillustrative and not limiting. The scope of the present invention isindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are intended to be embraced therein.

INDUSTRIAL APPLICABILITY

The silicone adhesive composition according to the present invention canbe used in the same applications as conventional silicone adhesivecompositions. The adhesive tape according to the present invention canbe used in the same applications as conventional adhesive tapes.

The invention claimed is:
 1. A silicone adhesive composition consistingessentially of: 100 parts by weight of a peroxide-curable silicone; 1.2to 3.2 parts by weight of an organic peroxide curing agent; and 2 to 9parts by weight of an addition reaction-curable silicone rubber, whereinthe peroxide-curable silicone includes (1) at least one selected fromthe group consisting of a dimethylpolysiloxane which may optionally havea hydroxy group, and a partial condensate thereof and (2) and at leastone selected from an MQ resin which is comprises an M unit and a Q unit,and a partial condensate thereof, the addition reaction-curable siliconerubber contains an addition-polymerizable group, and the siliconeadhesive composition satisfies at least one of the following conditions:(a) a gel fraction of a cured product of the silicone adhesivecomposition is 40 to 60%; or (b) in an adhesive tape comprising a baseand an adhesive layer placed on the base, the adhesive layer beingformed from the silicone adhesive composition, an amount of peel in 90°direction is 0 (mm), wherein the amount of peel in 90° direction isdetermined by: (i) cutting the adhesive tape to obtain a 10-mm-wide testspecimen; (ii) attaching the test specimen to a stainless steel plate sothat an adhesive area is 10 mm×20 mm and one edge of the test specimenis not in contact with the stainless steel plate; (iii) applying a loadof 20 g, acting in a direction perpendicular to the surface of thestainless steel plate, to the one edge of the test specimen; (iv)quickly heating the test specimen and the stainless steel plate to 250°C. and holding at 250° C. for 1 hour; and (v) evaluating an amount ofpeel of the test specimen.